I have found that substitute is probably the best move on boosting sweepers. It blocks topsy turvy, parting shot, prankster spore, and imposter, as well as preventing the fake out flinch and absorbing other attacks. Substitute is very useful, because it also lets you scout, and it has great synergy with spore. Once you have a sub up, magic bounce and magic coat don't cause you to put yourself go sleep, making spore and even dark void much better options. Spore helps get around unawares, and I often run mold breaker to help spore and kill sheddy. Of course, it isn't feasible to run all of this on one sweeper, because then you have two move slots to attack and boost, but all of these have helped sweepers that I have used in the past.Magic Bounce is probably my favorite of these to have on sweepers because you can basically boost unimpeded by status conditions, Whirlwind, or Prankster annoyance. The main things that can stop a Magic Bounce sweeper from boosting and sweeping are Shedinja, Mold Breaker (a very good counter to this strategy), Heart Swap (a really good move that no one uses anymore), and Haze (again, no one uses it). (You can be Psycho Shifted or Tricked something, but that won't be too much of a detriment.)
Any kind of boosting is relatively weak to Imposter, so I use a standard anti-Imposter Ghost type.
One thing that really hurt set up sweeping was the tendency towards hyper offense, especially before parental bond was banned. Boomburst goes through sub, safety goggles curbs many a free set up, and extremespeed/fake out are both strong enough to punch stuff in the face once the sub is gone. I haven't played much with trying to get sweepers around those, probably because I haven't played much in general, but I like the idea of boosting sweepers being better in general. Sniper seems like a very strong ability, a pity that dragons now have to deal with fairies.
What sets are the PH gigas running these days?